The present invention relates to a flexible wiring board for use in operating panels of various kinds of electronic equipment and its fabrication method.
One method of the prior art flexible wiring board fabrication is removing unnecessary portions of copper foil by etching from a flexible board on which copper foil is pasted, and leaving circuit portions of the copper foil to form a conductive circuit.
Another method of the prior art flexible wiring board fabrication is by printing a circuit pattern on a flexible board with use of a conductive paste which was prepared by dispersing conductive powders such as a silver powder or the like into resin varnish and baking the printed pattern to complete a conductive circuit layer.
However, in the case of the flexible wiring board that uses copper foil, the disposition of the waste solution released from a etching process is costly and the environmental contamination problems caused by disposing harmful waster solution tend to become serious. Besides, the copper foil raises a question of insufficient durability against bending strains.
In the case of the flexible wiring board that uses a conductive paste to form a printed conductive circuit, there are questions of high resistance of the circuit pattern, inferior quality of the circuit, and poor solderability of the printed conductive circuit.